RE: Mersenne: Hitting the snail...

[Will Edgington]

   I suppose the factoring methods do not guarantee to find _prime_
   factors.

Correct.  In fact, I recently added the ecmfactor program to the mers
package precisely because other programs, notably Factor98 (which uses
the P-1 method), print composite factors.  I use ecmfactor routinely
(once a week or so) to factor a composite factor discovered by someone
else using Factor98.

Ecmfactor uses the freeLIP library's ECM (Elliptic Curve Method)
functions to factor arbitrary natural numbers.  Ecm3 uses the same
functions to factor Mersenne number cofactors (the part left after
some known factors are divided out).

                                                        Will